It is known that fructose is substantially sweeter than glucose. Because the latter is relatively inexpensive and readily available, it is desirable to have an efficient and economical means of converting glucose to fructose. The alkali isomerization of glucose yields fructose, but the production of undesirable side products and the necessity of removing caustic and other materials from a food ingredient make this route unattractive. A preferred method of isomerization utilizing enzymes has the advantages of specificity of reaction and lesser likelihood of producing undesirable side products which must be removed before the fructose-containing material can be used in foods. The enzymes which effect the conversion of glucose to fructose are called glucose isomerases and are formed from such bacteria belonging, inter alia, to the genus Arthrobacter and the genus Actinoplanes. These enzymes are water soluble, and if they are merely added to aqueous solutions of glucose, recovery of enzyme for reuse is difficult and expensive. Using the enzyme only once also affords a process which is relatively expensive. Consequently, many techniques have been developed for immobilizing the enzyme in such a way that substantial enzymatic activity in isomerizing glucose to fructose is displayed while the enzyme itself remains rigidly attached to some water-insoluble support, thereby permitting reuse of the enzyme over substantial periods of time and for substantial amounts of glucose-containing solutions. One illustration of a method for immobilizing an enzyme is found in Levy and Fusee, U.S. Pat. No. 4,141,857, where a polyamine is adsorbed on a metal oxide such as alumina, the resulting composite is treated with an excess of bifunctional reagent, such as glutaraldehyde, so as to crosslink the amine, thereby entrapping the resulting polymer in the pores of the metal oxide, and thereafter contacting the mass with an enzyme to form covalent bonds between the pendant aldehyde groups and a amino groups on the enzyme. It is highly desirable that the material used in making immobilized enzyme contain the desired enzyme, here glucose isomerase, in as chemically pure a state as possible, both to assure maximum loading on the support, and to assure that the immobilized enzyme product will be homogeneous in the kind of enzyme bound to the support, thereby insuring maximum specificity in the conversion of glucose to fructose.